MediaElement.js is an HTML5 <audio> or <video> player with support for MP4, WebM, and MP3 as well as HLS, Twitch, YouTube, Facebook, SoundCloud and others with a common HTML5 MediaElement API, enabling a consistent UI in all browsers.
The video extension also supports subtitles!
More information
https://www.wysiwygwebbuilder.com/mediaelement.html
You can download the new extension via the Extension Manager: Menu->Tools->Extension Manager->Online Gallery->Audio and Sound
Please read the included (PDF) document for help.